The invention disclosed herein pertains generally to electromagnetic transducers, and more particularly to an electromagnetic transducer for the drive of a quartz crystal controlled electric clock, which drive includes a permanent mangetic rotor and a stator unit having at least one excitation coil.
The stator unit of standard electromagnetic transducers is commonly formed from several differently designed components, which components are used as mounts for the excitation coils and which components may be manipulated in order to adjust the air gap between the stator and the rotor to a desired value. Prior art electromagnetic transducers are known, such as the one disclosed in the published German patent application No. 11 24 591, where the stator unit consists of two dissimilar halves which form a butt-joint in the area of the position of the excitation coil. Such electromagnetic transducers have a relatively high magnetic resistance due to the air gap between the butt-joined components so that the efficiency of such electromagnetic transducers is reduced. Furthermore, the production costs of such electromagnetic transducers are relatively high because of the need to utilize dissimilar components and because of the need for relatively great precision in the manufacture of the stator components in the region of the butt-joint in order to minimize the size of the air gap in this region.
Accordingly, a primary object of the present invention is to provide an electromagnetic transducer for the drive of an electric clock where the stator unit includes relatively few components in order to reduce production costs.
Another object of the present invention is to provide an electromagnetic transducer wherein the magnetic resistance of the stator circuit is relatively low, resulting in a saving of energy and/or an increase in the torque available to the rotor.
An electromagnetic transducer, according to the present invention, includes a stator unit having two, mirror-image stator sections. Each of the stator sections has a generally C-shaped contour, i.e. each of the stator sections includes a central element to which is integrally connected an upper arm and a lower arm. Each of the upper arms of the two stator sections has an end face having a semicircular groove. When the two stator sections are joined together, the semicircular grooves in the upper arms of the stator sections combine to form a generally circular aperture which receives a rotor.
When the stator is assembled, the lower arms of the two stator sections overlap at what is the magnetic junction of the stator. The area of the overlap is relatively large. In the overlap region each of the lower arms of the two stator sections lies in a plane parallel to the plane of the stator, but offset from the plane of the stator by one-half the thickness of the arm. The offset of the lower arm of one stator section is in a direction opposed to the offset of the lower arm of the other stator section. A coil winding is arranged about the lower arms of the two stator section, in the vicinity of the overlap region.
Each of the stator sections also includes a leg or projection which projects from the point of intersection of the central element and the lower arm of the stator section. These projections each include an aperture which aids in the adjusting and fastening of the stator sections.
The present invention is advantageous because the stator unit of the electromagnetic transducer is made up of two identical sections. Because the sections are identical, the cost of manufacture is relatively low, and the process of assembly is relatively simple.